This invention relates generally to apparatus and methods for use in well completions and, more particularly, is operable for multiple purposes during the insertion and cementing of tubular strings such as casing and liners in the well bore.
For instance, in vertical or horizontal boreholes, or sections of a well having vertical and horizontal boreholes, one or more casing strings may be lowered into the hole and anchored therein by pumping a column of cement into the annulus between the casing string and the wall of the borehole. When lowering casing/liner into the wellbore, it has become conventional practice to fill the casing/liner string with drilling fluid. However due to the volume displaced by the tubular string, surge pressure is created during the process of lowering the casing into the fluid filled wellbore. The surge pressure may damage the formation as fluid is highly compressed and forced into the formation. The surge pressure may be especially great when running close tolerance casings or liners. While devices have been used to permit fluid flow into the casing as it is lowered to thereby reduce surge pressure, problems may still occur due to limited internal casing diameters that restrict the volume of fluid flow and/or restrictions in the casing internal diameter due, for instance, to the internal diameter of float valves in the float equipment. Moreover, cuttings from the well bore may collect and bridge, for instance adjacent restrictions in the casing string, to create additional problems. Moreover, damage may occur to internal elements such as hydraulically activated liner hanger equipment, float valves, sealing elements such as seats for the float valves, or other elements, due to the abrasive fluids or cuttings from the wellbore that flow into the casing string.
When the casing string has been placed at the desired depth and is being held at the surface or placed on a hanger from a previously set casing string of larger diameter, a wiper plug may be launched into the casing/liner string. Cement may be pumped into the string above the wiper plug (called a bottom plug). The bottom plug forms a barrier that separates the cement above the bottom plug from the mud which may be below the bottom plug. Pumps at the surface are used to pump the mud, and then the cement out of the lower end of the string and/or past a float shoe, or float collar, or well tool having a back pressure valve, at its lower end and into the casing/well bore annulus. It should be mentioned that if the back pressure valve or float shoe is located at the bottom end of the casing string, the device is sometimes referred to as a float shoe. If this device is used interiorly to the length of a full casing string, the device is sometimes referred to as a float collar. Thus, one nomenclature difference in these types of devices depends on whether the device is threaded to the casing on one end (shoe), or on both ends (collar). As used herein, float equipment refers to equipment typically positioned near or adjacent the bottom of the tubular string such as casing or liner which contains valves that may be used to control back pressure that might permit cement to flow back into the casing/liner after cementing.
When the wiper plug lands on the float shoe/collar, increased pumping pressure may be used to burst or rupture a frangible diaphragm across the interior of the wiper plug to permit the cement which was above the wiper plug to be pumped into the annulus. The back pressure valve in the float shoe/collar prevents the cement positioned in the annulus from simply re-entering the casing into any cement ports below the valve after pumping stops. After the desired amount of cement has been pumped into the annulus and has been allowed to set a drilling tool may be lowered into the casing string and used to drill out the plug (or plugs) and the float shoe/collar containing the back pressure valve. This opens the lower end of the casing string, if desired, for further drilling.
Some float shoes have fluid jets, or directed openings, facing downwardly for assisting lowering of casing into place by providing downwardly directed mud jets during the casing run in to assist circulating out or washing rock cuttings present in the uncased section of borehole that might prevent the casing being lowered. The downwardly facing jets assist in moving any remaining rock cuttings in the well bore to be circulated out of the well via the annulus between the casing and borehole wall during the run in operation. Some such tools used as float shoes have had upwardly facing fluid ports or jets to assist in the distribution of cement into the borehole/casing annulus once the tool is in place. Although either of the jets are useful, float shoes having both types of fluid ports or jets are less effective because the operation of one naturally interferes with the operation of the other. Thus, it has been desirable to have one type of ports or the other but not both.
In one type of float shoe, one or more back pressure valves (or one way valves) may be positioned in place by cementing the valves into a short piece of pipe threaded to the end (when used as a shoe) or to a section between casing lengths (when used as a collar) of the casing string. These check valves prevent the re-entry of cement or mud interiorly to the casing during the run in and cementing operation.
Thus, downwardly facing ports or jets have been found useful during casing run in whereas upwardly facing jets promote the equal circumferential distribution of cement when cementing takes place. The upwardly facing jets create turbulence in the casing/borehole annulus and this tends to promote desired circumferential distribution of cement about the annulus. However, the use of both downwardly and upwardly facing jets dilutes the function of each type of jet.
The inventors have conceived that it would be desirable to optimize both the run in and the cementing operation with a float shoe or float collar that has jets directed downwardly during the run in, but then has jets directed in an upward direction during the cementing operation. If this optimization were accomplished, as discussed subsequently herein, the run in and cementing operations would be safer, more reliable, more economical, faster, and more efficient. Moreover, it would be desirable to somehow limit damage to internal components such as float valves and seating elements that may be damaged by flow of abrasive fluids that contain cuttings. Those skilled in the art will appreciate the present invention which provides solutions to the problems discussed hereinbefore.
Thus, the apparatus of the present invention may comprise a float shoe or float collar that incorporates a check valve, or a plurality of such valves, which can allow the casing to fill up from the bottom with well fluid (auto fill) during run in. Below the valve, or valves, may be a center outlet hole as well as both upwardly and downwardly facing jets. In one embodiment, a tube inside the float shoe holds the flapper or check valve(s) open to allow fluid into the casing or to permit circulation. This same tube also covers and closes a set of upwardly facing jets during run in. The downwardly facing jets are open to aid in washing the borehole wall during the casing run in or float in. Once the casing string has reached the desired depth, a drop member such as an obscuration ball may be pumped down the casing. The ball seats in the float shoe or float collar tube. With an increase in pumping pressure from the surface, the seated ball then causes the float shoe or float collar tube to move downwardly inside the tool. The downward movement allows the check valve(s) or flappers to swing closed, thus activating the check valve(s). When the tube shifts downwardly it closes and shuts off the downwardly facing jets and exposes, or opens, the upwardly facing jets to assist in cement distribution, during the cementing operation, to all sides of the casing.
The well completion equipment may further comprise one or more valve seats positioned between the outer tubular member and the inner tubular member. In one embodiment of the invention, the inner tubular member is moveable with respect to the outer tubular member from a first position to a second position for uncovering the valves and the valve seats. The outer tubular member may define one or more passageways which are blocked by the inner tubular member in the first position. The one or more passageways may be opened to permit fluid flow from within the tubular string to outside of the tubular string when the inner tubular member is moved from the first position to a second position.
The well completion float equipment may further comprise a seat secured to the inner tubular member for receiving a drop member. In one embodiment, the valves may comprise a plurality of flapper valves. The one or more valves may be held in an open position when the inner tubular member is in the first position.
The present invention may comprise an outer tubular member forming a portion of the tubular string and having at least one first opening therein and at least one second opening therein. The at least one first opening and the at least one second opening may provide a passageway between the inside and the outside of the tubular string. A moveable member may be provided which is moveable from a first position to a second position such that the moveable member blocks the at least one first opening in the first position. The moveable member may block the at least one second opening in the second position.
The well completion float equipment may further comprise one or more valve seats which may be insulated from fluid flow in the first position and may be selectively engageable with fluid flow in the second position.
In another embodiment, the well completion float equipment may also comprise a drop member mounted adjacent to the moveable member. The drop member may be operable in response to fluid pressure for engaging the moveable member.
The invention may also comprise a method for completing a well with float equipment and may be operable for use in lowering a tubular string into a wellbore. The method may comprise steps such as, for instance, covering one or more valves such that the valves are held in an open position and insulated from fluid flow through the tubular string, and selectively uncovering the valves for controlling back pressure in the tubular string.
The step of selectively uncovering may further comprise dropping a member into the tubular string. Other steps of the method may include selectively closing one or more passageways between the inside of the tubular string and the outside of the tubular string.
In one embodiment, the method may comprise steps such as blocking one or more up jets while running the tubular string into the wellbore, and selectively unblocking the one or more up jets to pump fluid in an upwardly direction with respect to the tubular string through the one or more up jets. The method may further comprise selectively blocking one or more down jets and/or selectively exposing one or more check valves to fluid pressure. The method may also comprise selectively blocking a passageway through a bottom end of the float equipment.
Thus, the apparatus of the present invention may comprise a float shoe or float collar that incorporates a check valve, or a plurality of such valves, which can allow the casing to fill up from the bottom with well fluid (auto fill) during run in. Below the valve, or valves, may be a center outlet hole as well as both upwardly and downwardly facing jets. In one embodiment, a tube inside the float shoe holds the flapper or check valve(s) open to allow fluid into the casing or to permit circulation. This same tube also covers and closes a set of upwardly facing jets during run in. The downwardly facing jets are open to aid in washing the borehole wall during the casing run in or float in. Once the casing string has reached the desired depth, a drop member such as an obscuration ball may be pumped down the casing. The ball seats in the float shoe tube. With an increase in pumping pressure from the surface, the seated ball then causes the float shoe tube to move downwardly inside the tool. The downward movement allows the check valve(s) or flappers to swing closed, thus activating the check valve(s). When the tube shifts downwardly it closes and shuts off the downwardly facing jets and exposes, or opens, the upwardly facing jets to assist in cement distribution, during the cementing operation, to all sides of the casing.
In another embodiment, a multi-purpose method is provided for completing a well having a tubular string therein. The method comprises steps such as providing a receptacle within the tubular string for receiving a drop member, providing a breakable member for the receptacle such that the breakable member breaks at a selected first pressure, and providing pressure responsive equipment in the tubular string at a well depth above the receptacle. The pressure responsive equipment could be any hydraulically operated equipment such as, for instance, hydraulically operated liner hanging equipment. The pressure operated equipment is operable at a second pressure whereby the first pressure is greater than the second pressure.
Other steps may include releasing the drop member so that it can seal the receptacle. Steps may then include pumping into the tubular string to produce a second pressure in the tubular string so as to thereby operate the pressure responsive equipment in the well, and then subsequent to operating the pressure responsive equipment, pumping into the tubular string to produce the first pressure for breaking the breakable member.
Moreover, the method may include utilizing pressure applied to the drop member to uncover one or more valves for controlling fluid flow through the tubular string, and/or utilizing pressure applied to the drop member to block off fluid flow from one or more down jets, and/or utilizing pressure applied to the drop member to open one or more up jets to thereby provide fluid flow through the up jets.
Other steps may include pumping fluid through said receptacle for circulating fluid within said well prior to releasing the drop member. For instance, this may include pumping fluid through down jets prior to releasing the drop member.
The invention may be best understood by reference to the detailed description thereof which follows and by reference to the appended drawings. The drawings are intended to be illustrative of the preferred embodiment of the invention but are not intended to be limitative of the invention as the invention may admit to several embodiments.